It is way less grindy than some games.

No where near the level of Monster Hunter or any korean mmo.
Less grindy than stalker kills in Killing Floor.

The reward for work isn't really all that bad. If you logistically plan base locations for processing ore the only really one that feels a bit grindy is black forest bronze.
People complain about Iron but frankly I find that one faster than most. Silver, to me, is the easiest. Black metal gets delivered as drops from kills as well so you don't even mine it.
edit add - since the changes to how the pickax works mining iron and silver is so much faster than before H&H since it will hit all things the swing arc passes through. So instead of swinging and getting one surface hit you get multiple hits in one swing. The sludge piles in the iron crypts just melt now. And the multiple hits means less stamina used per drop and more xp gain per swing.

Growing food isn't bad as well... you only need to find one set of seeds to plant.. then you can plant the item for more seeds. 3 for 1 so you build up fairly quickly and crops only need to be planted and forgotten... no tending needed through to harvest.

I think a lot of the complaints come from people who play shooters or just want to kill bosses and be done with the game. So any grind they would complain about. But that is the thing though...the game does attract all kinds of players who do find it fun. Just some of the details are not what they are used to.